/test.mp3:
# ffmpeg -f lavfi -i sine -t 10ms test.mp3
$ fq -d mp3 '.frames[0].xing | ., .frames, .toc, .header, .present_flags.toc, .missing' /test.mp3
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |.frames[0].xing: {} (xing)
0x40|      49 6e 66 6f                              |  Info          |  header: "Info"
0x40|                  00 00 00 0f                  |      ....      |  present_flags: {}
0x40|                              00 00 00 02      |          ....  |  frames: 2
0x40|                                          00 00|              ..|  bytes: 599
0x50|02 57                                          |.W              |
0x50|      00 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6|  ..............|  toc: [100]
0x60|a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6 a6|................|
*   |until 0xb5.7 (100)                             |                |
0xb0|                  00 00 00 00                  |      ....      |  quality: 0
0xb0|                              4c 61 76 63 35 38|          Lavc58|  lame_extension: {}
0xc0|2e 39 31 00 00 00 00 00 00 00 00 00 00 00 00 24|.91............$|
0xd0|05 07 00 00 00 00 00 00 02 57 62 f0 5a 35      |.........Wb.Z5  |
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |
0x40|                              00 00 00 02      |          ....  |.frames[0].xing.frames: 2
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |.frames[0].xing.toc: [100]
0x50|      00                                       |  .             |  [0]: 0
0x50|         a6                                    |   .            |  [1]: 166
0x50|            a6                                 |    .           |  [2]: 166
0x50|               a6                              |     .          |  [3]: 166
0x50|                  a6                           |      .         |  [4]: 166
0x50|                     a6                        |       .        |  [5]: 166
0x50|                        a6                     |        .       |  [6]: 166
0x50|                           a6                  |         .      |  [7]: 166
0x50|                              a6               |          .     |  [8]: 166
0x50|                                 a6            |           .    |  [9]: 166
0x50|                                    a6         |            .   |  [10]: 166
0x50|                                       a6      |             .  |  [11]: 166
0x50|                                          a6   |              . |  [12]: 166
0x50|                                             a6|               .|  [13]: 166
0x60|a6                                             |.               |  [14]: 166
0x60|   a6                                          | .              |  [15]: 166
0x60|      a6                                       |  .             |  [16]: 166
0x60|         a6                                    |   .            |  [17]: 166
0x60|            a6                                 |    .           |  [18]: 166
0x60|               a6                              |     .          |  [19]: 166
0x60|                  a6                           |      .         |  [20]: 166
0x60|                     a6                        |       .        |  [21]: 166
0x60|                        a6                     |        .       |  [22]: 166
0x60|                           a6                  |         .      |  [23]: 166
0x60|                              a6               |          .     |  [24]: 166
0x60|                                 a6            |           .    |  [25]: 166
0x60|                                    a6         |            .   |  [26]: 166
0x60|                                       a6      |             .  |  [27]: 166
0x60|                                          a6   |              . |  [28]: 166
0x60|                                             a6|               .|  [29]: 166
0x70|a6                                             |.               |  [30]: 166
0x70|   a6                                          | .              |  [31]: 166
0x70|      a6                                       |  .             |  [32]: 166
0x70|         a6                                    |   .            |  [33]: 166
0x70|            a6                                 |    .           |  [34]: 166
0x70|               a6                              |     .          |  [35]: 166
0x70|                  a6                           |      .         |  [36]: 166
0x70|                     a6                        |       .        |  [37]: 166
0x70|                        a6                     |        .       |  [38]: 166
0x70|                           a6                  |         .      |  [39]: 166
0x70|                              a6               |          .     |  [40]: 166
0x70|                                 a6            |           .    |  [41]: 166
0x70|                                    a6         |            .   |  [42]: 166
0x70|                                       a6      |             .  |  [43]: 166
0x70|                                          a6   |              . |  [44]: 166
0x70|                                             a6|               .|  [45]: 166
0x80|a6                                             |.               |  [46]: 166
0x80|   a6                                          | .              |  [47]: 166
0x80|      a6                                       |  .             |  [48]: 166
0x80|         a6                                    |   .            |  [49]: 166
    |                                               |                |  [50:99]: ...
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |
0x40|      49 6e 66 6f                              |  Info          |.frames[0].xing.header: "Info"
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |
0x40|                           0f                  |         .      |.frames[0].xing.present_flags.toc: true
null
$ fq -d mp3 '.frames[0].xing | ., .frames, .toc, .header, .present_flags.toc, .missing | tovalue' /test.mp3
{
  "bytes": 599,
  "frames": 2,
  "header": "Info",
  "lame_extension": {
    "abr_vbr": 0,
    "audiophile_replay_gain": 0,
    "encoder": "Lavc58.91",
    "encoder_delay": 576,
    "encoder_padding": 1287,
    "lame_ath_type": 0,
    "lame_flags": 0,
    "length": 599,
    "lowpass_filter": 0,
    "misc": 0,
    "mp3_gain": 0,
    "music_crc": 25328,
    "preset": 0,
    "radio_replay_gain": 0,
    "replay_gain_peak": 0,
    "tag_crc": 23093,
    "tag_revision": 0,
    "vbr_method": 0
  },
  "present_flags": {
    "bytes": true,
    "frames": true,
    "quality": true,
    "toc": true,
    "unused": 0
  },
  "quality": 0,
  "toc": [
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  ]
}
2
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]
"Info"
true
null
$ fq -d mp3 '.frames[0].xing | ., .frames, .toc, .header, .present_flags.toc, .missing | tovalue' /test.mp3
{
  "bytes": 599,
  "frames": 2,
  "header": "Info",
  "lame_extension": {
    "abr_vbr": 0,
    "audiophile_replay_gain": 0,
    "encoder": "Lavc58.91",
    "encoder_delay": 576,
    "encoder_padding": 1287,
    "lame_ath_type": 0,
    "lame_flags": 0,
    "length": 599,
    "lowpass_filter": 0,
    "misc": 0,
    "mp3_gain": 0,
    "music_crc": 25328,
    "preset": 0,
    "radio_replay_gain": 0,
    "replay_gain_peak": 0,
    "tag_crc": 23093,
    "tag_revision": 0,
    "vbr_method": 0
  },
  "present_flags": {
    "bytes": true,
    "frames": true,
    "quality": true,
    "toc": true,
    "unused": 0
  },
  "quality": 0,
  "toc": [
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  ]
}
2
[
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]
"Info"
true
null
$ fq -d mp3 '.frames[0].xing | ., .frames, .toc, .header, .present_flags.toc, .missing | type' /test.mp3
"object"
"number"
"array"
"string"
"boolean"
"null"
$ fq -d mp3 '.headers | length, type' /test.mp3
1
"array"
$ fq -d mp3 '.headers | tostring' /test.mp3
exitcode: 5
stderr:
error: tostring cannot be applied to: array
$ fq -d mp3 '.headers | tonumber' /test.mp3
exitcode: 5
stderr:
error: tonumber cannot be applied to: array
$ fq -d mp3 '.headers[0] | tostring' /test.mp3
exitcode: 5
stderr:
error: tostring cannot be applied to: object
$ fq -d mp3 '.headers[0] | tonumber' /test.mp3
exitcode: 5
stderr:
error: tonumber cannot be applied to: object
$ fq -d mp3 '.headers[0].version | tonumber' /test.mp3
4
$ fq -d mp3 '.headers[0].version | tostring' /test.mp3
"4"
$ fq -d mp3 '.headers[0].magic | tonumber' /test.mp3
exitcode: 5
stderr:
error: invalid number: "ID3"
$ fq -d mp3 '.headers[0].magic | tovalue, length, tostring, type' /test.mp3
"ID3"
3
"ID3"
"string"
$ fq -d mp3 '.headers[0].magic[4]' /test.mp3
""
$ fq -d mp3 '.headers[0].magic[4:10]' /test.mp3
""
$ fq -d mp3 '.headers[10]' /test.mp3
null
$ fq -d mp3 '.headers[10:20]' /test.mp3
[]
$ fq -d mp3 '.headers[0].padding | tovalue, length, tostring, type' /test.mp3
null
0
"null"
"null"
$ fq -d mp3 '.headers[0].flags.unsynchronisation | tovalue, tostring, type' /test.mp3
false
"false"
"boolean"
# regresison null value (padding)
$ fq -d mp3 '.headers[0] | tovalue' /test.mp3
{
  "flags": {
    "experimental_indicator": false,
    "extended_header": false,
    "unsynchronisation": false,
    "unused": 0
  },
  "frames": [
    {
      "flags": {
        "compression": false,
        "data_length_indicator": false,
        "encryption": false,
        "file_alter_preservation": false,
        "grouping_identity": false,
        "read_only": false,
        "tag_alter_preservation": false,
        "unsync": false,
        "unused0": 0,
        "unused1": 0,
        "unused2": 0
      },
      "id": "TSSE",
      "size": 15,
      "text": "Lavf58.45.100",
      "text_encoding": 3
    }
  ],
  "magic": "ID3",
  "padding": null,
  "revision": 0,
  "size": 35,
  "version": 4
}
# test each in decoded order
$ fq -d mp3 '.headers[0][]' /test.mp3
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |
0x0|49 44 33                                       |ID3             |.headers[0].magic: "ID3" (Correct)
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |
0x0|         04                                    |   .            |.headers[0].version: 4
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |
0x0|            00                                 |    .           |.headers[0].revision: 0
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |.headers[0].flags: {}
0x0|               00                              |     .          |  unsynchronisation: false
0x0|               00                              |     .          |  extended_header: false
0x0|               00                              |     .          |  experimental_indicator: false
0x0|               00                              |     .          |  unused: 0
   |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |
0x0|                  00 00 00 23                  |      ...#      |.headers[0].size: 35
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |.headers[0].frames: [1]
0x00|                              54 53 53 45 00 00|          TSSE..|  [0]: {}
0x10|00 0f 00 00 03 4c 61 76 66 35 38 2e 34 35 2e 31|.....Lavf58.45.1|
0x20|30 30 00                                       |00.             |
    |00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f|                |
0x20|         00 00 00 00 00 00 00 00 00 00         |   ..........   |.headers[0].padding: Correct (none) (zero padding)